Physico-Chemical Features of Undoped and Fe/Cu-Doped Na0.67MnO2-Layered Cathodes for Sodium Batteries
, Maria Fittipaldi 3,4, Daniele Spada 1, Michela Sturini 1, Irene Quinzeni 5 and Marcella Bini 1,6,*
Round 1
Reviewer 1 Report
In the present manuscript, the authors have synthesized undoped and Cu or Fe doped Na0.67MnO2 samples as cathodes for SIBs via two different cooling methods, in which the Na0.67MnO2 sample prepared via slowly cooling suggested the highest capacity. In addition, they have deeply studied the physical/chemical features of electrode materials via various characterization techniques. However, there still exists some problems that need to be explained in more detail before being published in Applied Sciences.
Comment 1: The long-cycling performance of these cathodes is suggested, especially the NMO and the Fe02-Q cathodes.
Comment 2: In this study, the Na0.67MnO2 samples prepared via slowly cooling and without doping suggested the highest Na-storage performance, and we wonder what the significance of this work is. And what is the innovation of this work, compared with other similar studies?
Comment 3: More detailed Na-storage mechanism is suggested for the samples.
Comment 4: Why does the NMO suggest the highest electrochemical performance? Is it only induced by the high P2 content? And the authors are suggested to add more description on the relationship between the structure and electrochemical performance of the materials.
Author Response
see attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this manuscript, the authors fabricated undoped and Cu or Fe doped Na0.67MnO2 (NMO) by sol-gel route, with different cooling steps to room temperature, including natural cooling and quenching. By X-ray diffraction, it was demonstrated that Cu substitution had a positive effect for the structural stability. And spectroscopic techniques gave insights into the oxidation states of transition metals and suggestions about the magnetic ordering. In my opinion, the manuscript is interesting, but remains some problems. Therefore, I recommend it for publication after major revision.
In Figure 1, the PDF card corresponding to XRPD patterns was not shown. If possible, the XRPD results should be refined to prove the impurity sites and the contents of Fe and Cu elements.
There are some grammatical issues in the manuscript, such as singular and plural, and tense issues. Please check it again and revise.
In conclusions, it mentioned that “the introduction of substituents worsens the capacity values”. However, the rate capacity of Fe02-Q was the best among three quenched samples in Figures 9. Please carefully consider the accuracy of the words in manuscript.
The substitution of Cu plays a positive effect on structural stability, while the Fe02-Q show the best rate capacity among three quenched samples. Can the co-doping of Cu and Fe simultaneously optimize the structural stability and battery performance of the cathode material?
The structural stability, cooling method and electrochemical performance of different miscellaneous elements are explored in this paper, but it is not stated which material is the most competitive.
Some papers are related to this work and maybe helpful to the readers. (Adv. Energy Mater. 2019, 9, 1803342; Carbon Energy. 2021;3:615–626.;Carbon Energy. 2021;3:827;Advanced Energy Materials, 2020, 10, 2000927)
Author Response
see attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Authors have revised the manuscript carefully and all the questions raised have been addressed well. Therefore I recommend it for publication at the present form.
